The genetic determinants of hair texture in humans are largely unknown. Several human syndromes exist in which woolly hair comprises a part of the phenotype; however, simple autosomal recessive inheritance of isolated woolly hair has only rarely been reported…In all cases, we discovered pathogenic mutations in P2RY5, which encodes a G protein-coupled receptor and is a nested gene residing within intron 17 of the retinoblastoma 1 (RB1) gene. P2RY5 is expressed in both Henle’s and Huxley’s layers of the inner root sheath of the hair follicle. Our findings indicate that disruption of P2RY5 underlies ARWH and, more broadly, uncover a new gene involved in determining hair texture in humans.

Disease loci can tell us a lot about the normal range of human variation; the blue-eye gene was originally implicated in a form of albinism. So I got curious and popped P2RY5 into Haplotter, which detects recent selection events. Here’s what I found….

Here’s iHS:
And H:
Looks like there’s some action going on here. We’re looking at Yoruba (YRI), European (CEU) and East Asian groups (ASN) if you didn’t know. Here’s the table which shows p-values in the genomic region around this locus:

I was once suckered into giving a course on animal ecophysiology (I was told it was basic ecology until after it was too late to back out) which was a traumatic experience as I’ve only taken one university-level animal physiology course in my life. One of the students asked what the advantage is of kinky hair. I wondered if it might be a better insulator against the heat of the sun but that’s just guessing. I also said that perhaps the question should be the other way round – why do people have straight hair. Perhaps to shed rain more readily? I was hoping this post would answer the question. Are there any suggestions?

http://www.scienceblogs.com/gnxp razib

I was hoping this post would answer the question. Are there any suggestions?
100:1 odds that it has nothing to do with hair form as such. the variation in hair follicle thickness is due to a gene which is implicated in lots of developmental wackiness (see the EDAR link).

Niobe

Perhaps straight hair gave us an advantage when we moved to cooler climates and huddled together in fur clothing, so lice and fleas wouldn’t drive us crazy. Of course lice evolved along with our straight hair.
Now I find it odd / interesting that our body hair (genital, torso / limbs for men, armpits) didn’t go along with the smooth hair transition.

http://akinokure.blogspot.com agnostic

It’s either pleiotropic, and selection was for its effect on something else, or — what we would predict from Orr — selection acted on its effects at a bunch of places. It’s best if an allele helps adapt a population to a new environment by improving fitness through multiple phenotypes. There’s a new paper on adaptation in sticklebacks that shows this.
As for EDAR, at least one reason for selection was body odor — it’s involved in sweat glands. East Asians have an independent mechanism for suppressing body odor (the dry earwax allele), and common factors are never a coincidence. Now why East Asians were selected to not stink, I have a little hypothesis about…

http://www.scienceblogs.com/gnxp razib

Now why East Asians were selected to not stink, I have a little hypothesis about…
oh, i bet you do assman….

Richard Simons

Razib, thanks. It should have occured to me that a gene could have several different effects.

http://akinokure.blogspot.com agnostic

oh, i bet you do assman….
It doesn’t have to do with sex, attraction, or asses, if that’s what you were thinking…

Sandgroper

It doesn’t have to do with reality either.
Anyone who thinks East Asians don’t stink hasn’t been in the middle of a bunch of them who haven’t washed for a few days.

http://leherensuge.blogspot.com/ Luis

“I’ll let you figure out what’s going on with NUDT15….”
Epicanthic fold?

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Gene Expression

This blog is about evolution, genetics, genomics and their interstices. Please beware that comments are aggressively moderated. Uncivil or churlish comments will likely get you banned immediately, so make any contribution count!

About Razib Khan

I have degrees in biology and biochemistry, a passion for genetics, history, and philosophy, and shrimp is my favorite food. In relation to nationality I'm a American Northwesterner, in politics I'm a reactionary, and as for religion I have none (I'm an atheist). If you want to know more, see the links at http://www.razib.com